(a) Field of the Invention
The invention described herein relates to the field of chemistry and more particularly, to novel monoazo compounds useful in coloring edible compositions, in coloring textile fibers and in coloring cellulose; to processes for preparing said azo compounds and to the use thereof coloring edible compositions, coloring textile fibers and coloring cellulose.
(b) Information Disclosure Statement
There is a group of colorants which are approved by the U.S. Food and Drug Administration for incorporating into edible foodstuffs in the United States. Among the currently listed colorants are two red colorants, FD&C Red No. 3, which is a dyestuff of the xanthene class, and FD&C Red No. 40, which is a monoazo dyestuff. There are two additional azo dyestuffs, FD&C Red No. 2 and FD&C Red No. 4, which at one time had been approved as colors for edible compositions but over the years were removed from the list of approved colors. With the removal of FD&C Red No. 2, there was left a void in the colorants available for edible compositions for a single component blue-red colorant for edible uses and, in particular, a blue-red colorant which had stability in acidic compositions. The two remaining approved red colorants each have deficiencies which make them unacceptable for solving this problem. The colorant FD&C Red No. 3 is a blue-red, but has very poor stability in acidic compositions which have a pH lower than 4.2 and, depending upon the composition and its pH, will, over varying periods of time, turn colorless. FD&C Red No. 40 is a yellow-red and, even at high concentrations, will not impart a blue hue to compositions containing the colorant.
U.S. Pats. Nos. 3,519,617 and 3,640,733, which issued July 7, 1970 and Feb. 8, 1972, respectively, disclose yellow-red monoazo dyestuffs including FD&C Red No. 40 having the formula ##STR1## wherein R and R.sup.1 each represents lower alkyl of from 1 to 6 carbon atoms and M is hydrogen, ammonium or a physiologically acceptable metal cation, such as sodium, potassium, barium, calcium or iron. The azo dyestuffs are prepared by diazotizing the appropriate amine and coupling it to 2-hydroxynaphthalene-6-sulfonic acid and are disclosed as being useful to color edible composition.
Colour Index discloses as C.I. 14700 the yellow-red monoazo dyestuff having the formula ##STR2## which at one time was approved as FD&C Red No. 4 and used to color cherries. The monoazo dyestuff is prepared by diazotizing 3-amino-4,6-xylenesulfonic acid and coupling the diazo compound to 1-hydroxynaphthalene-4-sulfonic acid.
U.S. Pat. No. 3,578,652, which issued May 11, 1971, discloses a series of monoazo dyestuffs having the formula ##STR3## wherein R is an alkyl group of 1 to 6 carbon atoms, M is a hydrogen, ammonium or a physiologically acceptable metal cation, such as sodium, potassium, barium, calcium or iron and A is a monovalent radical selected from the group consisting of ##STR4## wherein M has the same definition as above. The azo dyestuffs are prepared by diazotizing the appropriate amine and coupling it to the desired naphtholdisulfonic acid. The dyestuffs are disclosed as being useful as colorants for foods, pharmaceuticals, cosmetics, and the like, and the aluminum lakes of the dyestuffs as pigments for plastics.
Colour Index discloses as C.I. 16185 the blue-red monoazo dyestuff having the formula ##STR5## which is also known as Amaranth and was formerly approved as FD&C Red No. 2 for use in edible compositions. The monoazo dyestuff is prepared by diazotizing 1-aminonaphthalene-4-sulfonic acid and coupling the resulting disazo compound to 2-hydroxynaphthalene-3,6-disulfonic acid.